# Spring Cloud Microservice Registration and Discovery

# Local Application Development

# Prerequisites

Before you start, please confirm that you have done the following:

Download Maven (opens new window) and set environment variables.
Download the latest Nacos Server (opens new window).
Follow the steps below to start Nacos server.
1. Unzip the Nacos server package.
2. Go to the nacos/bin directory and start Nacos server.

Tips

Linux/Unix/Mac system: sh startup.sh -m standalone
Windows system: double-click the file startup.cmd

# Create a Service Provider

Create an application project of service provider locally, add dependencies, enable service registration and discovery, and specify the register as Nacos server.

Create a Maven project named nacos-service-provider.

Add dependencies in the pom.xml file. Here takes Spring Boot 2.1.4.RELEASE and Spring Cloud Greenwich.SR1 as examples:

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath/>
    </parent>

    <dependencies>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            <version>2.1.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Greenwich.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

For Spring Cloud Greenwich, the corresponding Spring Cloud Alibaba version is 2.1.1.RELEASE.
For Spring Cloud Finchley, the corresponding Spring Cloud Alibaba version is 2.0.1.RELEASE.
For Spring Cloud Edgware, the corresponding Spring Cloud Alibaba version is 1.5.1.RELEASE.

Tips

The life cycle of the Spring Cloud Edgware version has ended, and it is not recommended to use this version to develop applications.

Create package: io.terminus.erda.trial.demo.hellospringcloud under the path src/main/java.

Create the startup class ProviderApplication of the service provider in package: io.terminus.erda.trial.demo.hellospringcloud, and add the following code:

package io.terminus.erda.trial.demo.hellospringcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

/**
 * @author erda
 */
@SpringBootApplication
@EnableDiscoveryClient
public class ProviderApplication {

    public static void main(String[] args) {
        SpringApplication.run(ProviderApplication.class, args);
    }
}

Tips

The annotation @EnableDiscoveryClient indicates that this application needs to enable service registration and discovery.

Create EchoController in package: io.terminus.erda.trial.demo.hellospringcloud, specify URL mapping as {/echo/{String}}, specify HTTP method as GET, obtain method parameter from the URL path and echo the received parameters.

package io.terminus.erda.trial.demo.hellospringcloud;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

/**
 * @author erda
 */
@RestController
public class EchoController {
    @RequestMapping(value = "/echo/{string}", method = RequestMethod.GET)
    public String echo(@PathVariable String string) {
        return string;
    }
}

Create application.yml under the path src/main/resources and add the following configuration to specify the address of Nacos server.
```
spring:
  application.name: service-provider
  cloud:
    nacos:
      discovery:
        server-addr: ${NACOS_ADDRESS:127.0.0.1:8848}
        namespace: ${NACOS_TENANT_ID:}
```
Tips

127.0.0.1 is the address of the Nacos server. If the Nacos server is deployed on another machine, change it to the actual IP address.
Verify the results.
Run the main function of ProviderApplication of nacos-service-provider to start the application.
Log in to the locally started Nacos server console http://127.0.0.1:8848/nacos (the default user name and password of the local Nacos console are both nacos).
In the left navigation bar, select Service Management > Service List, which already contains service-provider, and you can view detailed information as needed.

# Create a Service Consumer

Create a Maven project named nacos-service-consumer.

Add dependencies in pom.xml.

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4.RELEASE</version>
        <relativePath/>
    </parent>

    <dependencies>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            <version>2.1.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Greenwich.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

Create package: io.terminus.erda.trial.demo.hellospringcloud under the path src/main/java.

Configure RestTemplate and FeignClient in package: io.terminus.erda.trial.demo.hellospringcloud.

Create an interface class EchoService in package: io.terminus.erda.trial.demo.hellospringcloud, add @FeignClient annotation and configure the corresponding HTTP URL and HTTP method.

package io.terminus.erda.trial.demo.hellospringcloud;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * @author erda
 */
@FeignClient(name = "service-provider")
public interface EchoService {
    @RequestMapping(value = "/echo/{str}", method = RequestMethod.GET)
    String echo(@PathVariable("str") String str);
}

Create a startup class ConsumerApplication in package: io.terminus.erda.trial.demo.hellospringcloud and add the relevant configuration.

Use the @EnableDiscoveryClient annotation to enable service registration and discovery.
Use the @EnableFeignClients annotation to activate FeignClient.
Add @LoadBalanced annotation to integrate RestTemplate with service discovery.

package io.terminus.erda.trial.demo.hellospringcloud;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * @author erda
 */
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ConsumerApplication {

    @LoadBalanced
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class, args);
    }
}

Create a class TestController in package: io.terminus.erda.trial.demo.hellospringcloud to demonstrate and verify the service discovery function.

package io.terminus.erda.trial.demo.hellospringcloud;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @author edas
 */
@RestController
public class TestController {

    @Autowired
    private RestTemplate restTemplate;
    @Autowired
    private EchoService echoService;

    @RequestMapping(value = "/echo-rest/{str}", method = RequestMethod.GET)
    public String rest(@PathVariable String str) {
        return restTemplate.getForObject("http://service-provider/echo/" + str,
                String.class);
    }

    @RequestMapping(value = "/echo-feign/{str}", method = RequestMethod.GET)
    public String feign(@PathVariable String str) {
        return echoService.echo(str);
    }

}

Create application.yml under the path src/main/resources and add the following configuration to specify the address of Nacos server.
```
spring:
  application.name: service-consumer
  cloud:
    nacos:
      discovery:
        server-addr: ${NACOS_ADDRESS:127.0.0.1:8848}
        namespace: ${NACOS_TENANT_ID:}
```
Tips

127.0.0.1:8848 is the address of the Nacos server. If the Nacos server is deployed on another machine, change it to the actual IP address.
Verify the results.
Run the main function of ConsumerApplication of nacos-service-consumer to start the application.
Log in to the locally started Nacos server console http://127.0.0.1:8848/nacos (the default user name and password of the local Nacos console are both nacos).
In the left navigation bar, select Service Management > Service List, which already contains service-consumer and you can view detailed information as needed.

# Local Testing

Test the result of the consumer's service call to the provider locally.

Linux/Unix/Mac system

Please run the following commands:

curl http://127.0.0.1:18082/echo-rest/rest-rest
curl http://127.0.0.1:18082/echo-feign/feign-rest

Windows system

In your browser, enter http://127.0.0.1:18082/echo-rest/rest-rest and http://127.0.0.1:18082/echo-feign/feign-rest.

# Deploy the Application to Erda

When deploying an application to Erda, please note that the environment variables in the following configuration will be automatically injected.

spring:
  application.name: service-provider
  cloud:
    nacos:
      discovery:
        server-addr: ${NACOS_ADDRESS:127.0.0.1:8848}
        namespace: ${NACOS_TENANT_ID:}

spring:
  application.name: service-consumer
  cloud:
    nacos:
      discovery:
        server-addr: ${NACOS_ADDRESS:127.0.0.1:8848}
        namespace: ${NACOS_TENANT_ID:}

Modify dice.yml and add the dependency of register v2.0.

After the service is deployed, Erda will automatically inject two environment variables:

NACOS_ADDRESS
NACOS_TENANT_ID

Click on the registration center to view the registered services.